← Back to team overview

kicad-developers team mailing list archive

Re: Potential issues with oaa_ lib


On Mon, 30 Aug 2010, Alex G wrote:

:-p ). The most I'm planning to tackle is 200A at 7V switched from the
AC line.

Sounds interesting, especially the possible uses (please tell off the list ;) If 100Hz switcher counts, I've made such from (really)old telecom psu components about ten years ago. 70kgs with wheels, but _very_ difficult to break. Just some weeks ago I thought updating the controller design to the digital age and also replacing SCRs with synthetic mosfet ones to cut 300W from the losses. Fortunately I got my sanity back a few minutes later :)

What do you use for generating the artwork? I need to stick two
transparencies on top of each other to avoid pinholes. And if I'm lucky,
I get horizontal lines of toner going straight through the board, just
asking for a nice cutter-job after the board is etched.

I guess you are using a laser printer? Better UV-opacity is obtained with blue+yellow inkjet. I've seen some using it for 5mil work and that's amazing. They probably used better collimated light source than a led matrix though. I'm mostly doing toner transfers for prototypes with 12mil minimum width. Free laminate scrap helps...

The etch chemistry means a lot in home brew with inefficient agitation etc, and the finest + cheapest is stabilized sulphuric acid-hydrogen peroxide aka "peroxy-sulfuric" etch. Works very well unstirred, excellent etch quality (can be made even levelling or polishing) no fumes, just some very minor mist when etching is in progress due to peroxide decomposing. Stabilizers are usually phosphoric acid and phenol sulfonic acids at around 1g/l. Some aspirin dissolved in hot H2SO4 will do if phenol is unobtanium. Google will find a lot more details. Just remember to store all peroxide stuff in vented containers and remember that chlorides increase decomposition rate, so it may be wise not to use tap water for making the etch.

Before I forget to mention, the library discussion is very interesting :)

Follow ups